1. Field of the Invention
The invention relates to an India ink compensating chamber for capillary drafting pens. The compensating chamber serves as an expansion chamber between the India ink reservoir within the pen and the surrounding air.
The India ink compensating chamber in the case of capillary drafting pens in the event of an increase of inside pressure, absorbs India ink within an inside bore and/or within the India ink reservoir, such that India ink will not be forced out of the capillary writing tip due to excessive pressure. Furthermore, ambient air reaches the inside bore and the India ink reservoir by way of the India ink compensating chamber, whenever an underpressure develops in said reservoir due to consumption of India ink or a lowering of ambient temperature.
2. Description of the Prior Art
West German As No. 1,561,857 PA2 OS No. 2,216,015 PA2 OS No. 1,911,950
The conventional spiral-shaped India ink exchange chambers forming a capillary (German AS, No. 1,561,857, German OS No. 2,216,015) have well fulfilled the aforementioned tasks per se and are used at the present time in varied types of capillary drafting pens. It is true, however, that these India ink compensating chambers, due to their capillary shape, as well as the necessarily fine capillaries formed on the edges of the compensating chambers, as a result of the attaching thread and pen cover, are inclined to force the ink out of the reservoir and forwardly into the compensating chamber, that is to say underfined capillary forces develop.
These previously known India ink compensating chambers have moreover the disadvantage that only a single border surface is formed between the India ink and the air, which, in case of an aeration or expansion process, must be removed. The size of the meniscus radius forming in the ink within the compensating chamber and thus the resistance in case of aeration or expansion process is given as the result of the geometrical cross-section of the India ink compensation chamber. This resistance is very slight in the case of the previously known systems. Also, it is not possible to increase this resistance by decreasing the cross-section of the India ink compensation chamber, since capillary forces then occur, as a result of which the India ink is sucked into the India ink compensation chamber, that is to say the resistance becomes even slighter.